CRITICALITY AND SHIELDING

Other analytical methods are available to support more general nuclear plant operation such as ex-reactor fuel store management or radiation dosage evaluation, e. g. operations that require criticality or shielding modelling capabilities. These are described in this section; representative codes are shown in Table 16.6.

Monte Carlo techniques provide the most accurate way of determining the multiplication factor k-effective for systems containing fission. The MONK code (Smith et al., 2000) is one such code for determining nuclear criticality margins and safety.

Shielding codes such as MCBEND also use Monte Carlo techniques to determine radiation levels arising from nuclear sources (Wright et al., 1999). RANKERN represents a particular methodology for shielding using point kernel techniques for gamma-ray transport solutions (Chucas and Curl, 1999).

MCNP (NEA Annual Report, 2002) is another Monte-Carlo Code System for radiation dosimetry modelling. MCNPX extends this capability to high energy applications.

In terms of research requirements, these codes are relatively mature. Research is taking place to improve the numerical methods in these codes, and also in regard to extending their ranges of application to other nuclear systems.

In the next section, some of the model and code research and developments that are specific to evolutionary reactor systems are reviewed. Particular attention is paid to water reactors. There are some phenomena, particularly relating to the passive evolutionary systems, which are more important or new compared with existing plant and these therefore require further attention.

Table 16.6. Criticality and shielding

Phenomena

Computer code/model

Criticality

MONK

Shielding

MCBEND, RANKERN, MCMP

Table 16.7. Specific modelling for advanced water reactor safety analysis

Phenomena

Computer code/model

Zircaloy oxidation

SCDAP/RELAP5, ICARE/CATHARE, ATHLET-SA, MELCOR, MAAP

Boron-carbide reactions

SCDAP/RELAP5, MELCOR, MAAP

Aqueous fission products

MELCOR, MAAP

Inerted containment atmosphere

MELCOR, MAAP, JERICO, FUMO

Oxygen ingress into inerted

MELCOR, MAAP, CONTAIN

containment

Hydrogen effects on natural

MELCOR, MAAP

circulation

Heat exchange to the

CONTAIN, MAAP (AP-600)

containment shell

Direct containment heating

CONTAIN, MAAP

IAEA-TECDOC-752 (1994).

Добавить комментарий

Ваш e-mail не будет опубликован. Обязательные поля помечены *